Sheet feeding apparatus and image forming apparatus

ABSTRACT

A sheet feeding apparatus and an image forming apparatus are provided with a fixed member and a movable member, which regulate positions in a width direction of the sheet that is stacked on the dedicated cassette detachably attached to an intermediate plate, are provided while facing each other. The fixed member and the movable member moved to a position that regulates the sheet are regulated by side regulating members. The side regulating members that are movable in the width direction regulate the positions in the width direction of the sheet stacked on the intermediate plate.

This is a divisional of U.S. patent application Ser. No. 12/511,508filed Jul. 29, 2009 and allowed Mar. 3, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding apparatus and an imageforming apparatus, particularly to a sheet feeding apparatus in which asecond sheet stacking portion is detachably attached to a first sheetstacking portion and an image forming apparatus.

2. Description of the Related Art

Recently, an image forming apparatus such as a copying machine, aprinter, and a facsimile, in which the sheet is fed from the sheetfeeding apparatus to the image forming portion to form an image iswidely spread. Usually, in the sheet feeding apparatus, a sheet cassettethat is of a sheet storage portion is detachably attached to anapparatus main body, and the sheet stored in the sheet cassette isautomatically fed to the image forming portion.

In some of sheet cassettes used in the sheet feeding apparatus, anintermediate plate on which the sheets are stacked to press the sheetagainst a sheet feeding roller is provided while being able to be liftedand lowered. In the sheet cassette in which the intermediate plate isprovided, a trailing end regulating member that regulates a position ofa trailing end in a feeding direction of the sheet stacked and stored onthe intermediate plate (hereinafter referred to as trailing end) isprovided so as to store the sheets having different sizes. A side endregulating member is also provided to regulate a side end position in adirection (hereinafter referred to as width direction) orthogonal to thesheet feeding direction.

In the sheet cassette, the sheet trailing end is regulated by thetrailing end regulating member while the sheet side end is regulated bythe side end regulating member, whereby the sheet leading end is alwaysregulated at a predetermined position. Therefore, the sheet can stablybe fed irrespective of the sheet size when the sheet cassette is storedin the apparatus main body.

Recently, a demand to form an image in a small-size sheet that is of anirregular size sheet such as a 4-by-6-inch-size sheet and apostcard-size sheet in addition to a special sheet has been increased inthe image forming apparatus such as the laser beam printer.

However, for example, when the small-size sheet is set in the sheetcassette, the small-size sheet is located outside a range where the sideend regulating member and the trailing end regulating member are moved.Therefore, when the small-size sheet is set in the sheet cassette, theposition of the sheet cannot be regulated by the side end regulatingmember and the trailing end regulating member.

In order to regulate the small-size sheet whose position cannot beregulated by the regulating member, for example, Japanese PatentApplication Laid-Open No. 2005-263450 discloses a technique in which theside end regulating member can be moved to a position that regulates thesmall-size sheet. The intermediate plate is notched in the widthdirection in order to enable the side end regulating member to be movedin the width direction.

Japanese Patent Application Laid-Open No. 11-217123 discloses atechnique in which an attachment is attached to the side end regulatingmember. Japanese Patent Application Laid-Open No. 11-059925 discloses atechnique in which a dedicated cassette that is of a small-size-sheetregulating member is detachably attached to the sheet cassette.

However, in the conventional sheet feeding apparatus and image formingapparatus, when the intermediate plate is notched such that the side endregulating member can be moved in the width direction, it is necessarythat the intermediate plate is largely notched in order to enable theside end regulating member to be moved to the position that regulatesthe small-size sheet. When the attachment is attached to the side endregulating member, it is necessary that the attachment is moved to theside end position of the small-size sheet. Therefore, it is necessary tolargely notch the intermediate plate. A strength of the intermediateplate is decreased when the intermediate plate is largely notched.

On the other hand, when the dedicated cassette is detachably attached tothe sheet cassette, it is not necessary to largely notch theintermediate plate. However, the sheet cannot stably be fed because theside end regulating member that regulates the sheet position in thewidth direction is not provided in the dedicated cassette. Even if theside end regulating member is provided, a mechanism for fixing the sideend regulating member moved to a side end regulating position isrequired to stably feed the sheet. When the mechanism is provided, aconfiguration of the dedicated cassette becomes complicated and cost isincreased.

The present invention provides a sheet feeding apparatus and an imageforming apparatus, in which a sheet can stably be fed with a simpleconfiguration without decreasing strength of an intermediate plate.

SUMMARY OF THE INVENTION

A sheet feeding apparatus according to an aspect of the inventionincluding a sheet stacking portion on which a sheet is stacked; a pairof first regulating portions that is provided while being movable in awidth direction of the sheet in order to regulate a position in thewidth direction of the sheet stacked on the sheet stacking portion; asheet stacking unit that is attached to the sheet stacking portion; anda pair of second regulating portions that regulates the position in thewidth direction of the sheet stacked on the sheet stacking unit, whereinat least one of the second regulating portions is movable in the widthdirection, and the pair of second regulating portions are regulated bythe pair of first regulating portions, respectively.

Accordingly, the position of the second regulating member of the secondsheet stacking portion is regulated by the first regulating member thatregulates the position of the sheet stacked on the first sheet stackingportion, so that the sheet can stably be fed with the simpleconfiguration without decreasing the strength of the intermediate plate.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an entire configuration of a Laser Beam Printer (LBP)that is of an example of an image forming apparatus including a sheetconveying apparatus according to an embodiment of the invention.

FIG. 2 is a perspective view illustrating a sheet cassette that isdetachably attached to a printer main body of the laser beam printer.

FIG. 3 is a perspective view illustrating a configuration for moving aside regulating plate provided in the sheet cassette.

FIGS. 4A and 4B are perspective views illustrating an operation forstoring A5-size sheets in the sheet cassette.

FIG. 5 is a perspective view illustrating a state in which a dedicatedcassette is attached to the sheet cassette.

FIGS. 6A and 6B are first views illustrating a configuration of thededicated cassette.

FIG. 7 is a second view illustrating the configuration of the dedicatedcassette.

FIG. 8 is a perspective view illustrating a state in which small-sizesheets is set in the dedicated cassette.

FIGS. 9A and 9B illustrate an operation for regulating side endpositions of the small-size sheets stored in the dedicated cassette.

FIG. 10 illustrates a state in which an interference member exists abovea movable member provided in the dedicated cassette.

FIG. 11 illustrates a state in which the movable member is swung inabutting contact with the interference member.

FIG. 12 is a perspective view illustrating a different configuration ofthe dedicated cassette.

FIG. 13 is a perspective view illustrating a state in which thededicated cassette having the different configuration is attached to thesheet cassette.

DESCRIPTION OF THE EMBODIMENTS

An exemplary embodiment of the invention will be described in detailwith reference to the drawings.

FIG. 1 illustrates an entire configuration of a Laser Beam Printer (LBP)that is of an example of an image forming apparatus including a sheetconveying apparatus according to an embodiment of the invention.

Referring to FIG. 1, in a laser beam printer 50, a laser beam printermain body (hereinafter referred to as printer main body) 50A includes animage forming portion 50B, and a sheet feeding apparatus 50C is providedin a lower part of the printer main body 50A. The sheet feedingapparatus 50C feeds a sheet S, such as a recording sheet, which isstacked and stored in a sheet cassette 1 to the image forming portion50B.

The image forming portion 50B includes a process cartridge 57, and theprocess cartridge 57 includes a photosensitive drum 57 a, a charger 57b, a development sleeve 57 c, and a cleaner 57 d. The image formingportion 50B also includes a laser scanner 58 that is of exposure unitfor exposing a surface of the photosensitive drum 57 a to form anelectrostatic latent image on the photosensitive drum 57 a.

The printer main body 50A also includes a transfer roller 59 and afixing portion 60. The transfer roller 59 abuts on the photosensitivedrum 57 a, and the transfer roller 59 and the photosensitive drum 57 aconstitute a transfer portion. The fixing portion 60 fixes a tonerimage, transferred by the transfer portion, onto the sheet S.

The sheet feeding apparatus 50C includes the sheet cassette 1 and apickup roller 53. The sheet cassette 1 is of a sheet storage portionthat is detachably attached to the printer main body 50A. The pickuproller 53 delivers the sheets S stacked on the sheet cassette 1 from theuppermost side. The sheet feeding apparatus 50C also includes a pair ofretard rollers 54 a and 54 b that separates and conveys the sheet Sdelivered by the pickup roller 53.

Next, an image forming operation in the laser beam printer 50 configuredin this manner will be described.

When the image forming operation is started, the photosensitive drum 57a is rotated in an arrow direction, the surface of the photosensitivedrum 57 a is charged by the charger 57 b, and a laser beam is emitted tothe photosensitive drum 57 a from the laser scanner 58 based on theimage information. Therefore, electrostatic latent image is formed onthe photosensitive drum.

Then, toner that is properly charged according to the rotation of thedevelopment sleeve 57 c is supplied onto the photosensitive drum 57 a toadhere to the electrostatic latent image, whereby the electrostaticlatent image is developed and visualized as a toner image.

On the other hand, in parallel with the toner image forming operation,the pickup roller 53 is rotated to deliver the uppermost sheet S on thesheet cassette 1. The pair of retard rollers 54 a and 54 b conveys thesheet S delivered from the pickup roller 53, and a pair of registrationrollers 56 that is at a stop performs a leading end positioning (skewfeeding correction).

Then, in the image forming portion 50B, the pair of registration rollers56 conveys the sheet S to the transfer portion such that the sheet S istimed to the image formed on the photosensitive drum 57 a, and thetransfer roller 59 transfers the image of the photosensitive drum 57 ato the sheet S.

Then, the sheet S to which the toner image is transferred is conveyed toa fixing nip. The fixing nip includes a heating roller 60 a and apressure roller 60 b, which are provided in the fixing portion 60. Inthe fixing nip, the unfixed toner image is fixed to the sheet surface byheating and pressurization. A discharge roller 61 discharges the sheetS, to which the toner image is already fixed, onto a discharge tray 62.

As illustrated in FIG. 2, the sheet cassette 1 includes a cassette body5 and an intermediate plate 6. In the cassette body 5, a sheet storagespace 4 is formed to stack and store sheets having various sizes. Theintermediate plate 6 is of a first sheet stacking portion that isprovided to stack the sheets S while being able to be vertically swung.The intermediate plate 6 can be lifted and lowered about a swing shaft43 by a swing mechanism (not illustrated). The sheet cassette 1 includesside regulating members 7 and 8 and a trailing end regulating member 9.The side regulating members 7 and 8 are of a pair of width regulatingplates, and the pair of width regulating plates is of a first regulatingportion that regulates a side end position of the sheet. The trailingend regulating member 9 is of a regulating portion that regulates atrailing end position of the sheet.

The side regulating members 7 and 8 and the trailing end regulatingmember 9 are movable according to the sheet size. As illustrated in FIG.3, the side regulating members 7 and 8 include racks 46 and 47 that areengaged with a pinion 11, and the side regulating members 7 and 8 aremoved in opposite directions to each other by the same amount using theracks 46 and 47 and the pinion 11. The side regulating members 7 and 8are moved in opposite directions to each other by the same amount,thereby feeding the sheet based on the center of the sheet cassette 1.

FIG. 3 illustrates positions of the side regulating members 7 and 8 andtrailing end regulating member 9 when a large-size sheet, for example,an A4-size sheet is stored. When a small-size sheet, for example, anA5-size sheet is stored, each side of the side regulating members 7 and8 is moved in the direction in which one of the side regulating members7 and 8 is brought close to the other as illustrated in FIG. 4A.Therefore, the side regulating members 7 and 8 are moved toward thecenter of the sheet cassette 1.

After an A5-size sheet S1 is set between the side regulating members 7and 8, as illustrated in FIG. 4B, the trailing end regulating member 9is brought in abutting contact with the trailing end of the A5-sizesheet while the side regulating members 7 and 8 are brought in abuttingcontact with the side end of the sheet, whereby the side end positionand trailing end position of the A5-size sheet S1 are positioned tocomplete the setting of the sheet S1. Therefore, the positioning of thesheet S1 enables the sheet to be stably fed.

The sheet having the A5 size or more can be stored in the sheet cassette1. When a user prints a postcard, a cassette 30 that is of an attachmentdedicated to the small-size sheet is detachably attached to theintermediate plate 6 as illustrated in FIG. 5. For example, the cassettededicated to the small-size sheet (hereinafter referred to as dedicatedcassette) 30 can deal with the postcard-size, a 4-by-6-inch-size sheet,and a small-size sheet. A special sheet can also be stored in thededicated cassette 30.

As illustrated in FIGS. 6A and 6B, the dedicated cassette 30 that is ofa sheet stacking unit includes a sheet stacking portion 14, a latchingprojection 31, and four insertion units 23 to 26. The latchingprojection 31 is projected from a bottom of the sheet stacking portion14 and extended in an attaching direction. The latching projection 31and the four insertion units 23 to 26 are inserted from the attachingdirection into a latching opening 32 and insertion holes 23 a to 26 a,which are made in the intermediate plate 6 as illustrated in FIG. 2,which allows the dedicated cassette 30 to be detachably attached to theintermediate plate 6.

The dedicated cassette 30 includes a fixed member 19, a movable member13, and rear-side wall 20. The fixed member 19 is vertically provided onone of sides of the sheet stacking portion 14 and extended in the sheetfeeding direction. The movable member 13 is movable in the widthdirection along the sheet stacking portion 14. That is, in theembodiment, the dedicated cassette 30 includes the fixed member 19 andthe movable member 13, which are disposed as a second regulating portionwhile facing each other. The second regulating portion regulates theposition in the width direction of the sheet stacked on the dedicatedcassette 30. A small-size-sheet storage space 22 is formed by a bottomof the sheet stacking portion 14, the fixed member 19, the rear-sidewall 20, and the movable member 13.

As illustrated in FIG. 7, the movable member 13 is retained while beingable to swing with respect to the sheet stacking portion 14 by a shaft44, and the shaft 44 is supported in a frame (not illustrated) providedon the movable member side of the sheet stacking portion 14 while theshaft 44 and the movable member 13 are slidable in the width direction.

A hook portion 17 is provided in the movable member 13, and one of endsof a spring 12 that is of a biasing member is latched in the hookportion 17. The other end of the spring 12 is latched in a hook portion16 provided in the sheet stacking portion 14. In the movable member 13in which the spring 12 is latched, an end portion 13 a is brought inabutting contact with a receiving portion vertically provided in thesheet stacking portion 14 while biased by the spring 12, therebyregulating the position of the movable member 13.

FIG. 8 illustrates a state in which small-size sheets S2 is set in thededicated cassette 30. In a small-size sheet S2 set in the dedicatedcassette 30, one of the side end positions is regulated by moving themovable member 13 toward the fixed member side. The movable member 13 ismoved to press the small-size sheet S2 against the fixed member 19,thereby feeding the small-size sheet S2 based on one side of the fixedmember 19.

In FIGS. 8, 9A and 9B, movable-member hoods 34 and 35 are provided inthe movable member 13, and a hood 33 is provided in the fixed member 19.In feeding the sheet, the provision of the hoods 33 to 35 can preventthe small-size sheet S2 whose side end positions are regulated by themovable member 13 and fixed member 19 from deviating from the dedicatedcassette 30. In FIG. 8, 9A and 9B, fixed member receiving portions 37and 38 that are of a positioning portion are projected from an outsidewall surface of the fixed member 19, and movable member receivingportions 39 and 40 that are of the positioning portion are projectedfrom an outside wall surface of the movable member 13. Abutment surfaces37 a and 38 a and abutment surfaces 39 a and 40 a are formed into a flatshape. The abutment surfaces 37 a and 38 a abut on a regulating surface7 a that regulates the sheet in the side regulating member 7 of thefixed member receiving portions 37 and 38, and the abutment surfaces 39a and 40 a abut on a regulating surface 8 a that regulates the sheet inthe side regulating member 8 of the movable member receiving portions 39and 40. A distance T from a regulating surface 19 c that regulates thesheet of the fixed member 19 to the abutment surfaces 37 a and 38 a offixed member receiving portions (the positioning portions) 37 and 38 areset equal to a distance T from a regulating surface 13 c that regulatesthe sheet of the movable member 13 to the abutment surfaces 39 a and 40a of the positioning portions 39 and 40.

An operation for regulating the side end position of the small-sizesheet S2 stored in the dedicated cassette 30 will be described.

As illustrated in FIG. 8, the movable member 13 is moved to regulate theposition of the small-size sheet S2 set in the dedicated cassette 30,and the side regulating members 7 and 8 are moved in the widthdirection. Therefore, as illustrated in FIG. 9A, the fixed member 19 andthe movable member 13 moved to the position that regulates thesmall-size sheet S2 are sandwiched between the side regulating members 7and 8 while the fixed member receiving portions 37 and 38 and themovable member receiving portions 39 and 40 are interposed therebetween.

When the fixed member 19 and the movable member 13 are sandwichedbetween the side regulating members 7 and 8, the movable member 13 thatregulates the movement in the width direction of the small-size sheet S2can be prevented from deviating from the regulating position in feedingthe sheet. Therefore, the small-size sheet can stably be fed with thesimple configuration without largely notching the intermediate plate 6.

In the embodiment, as described above, the side regulating members 7 and8 are moved in the opposite directions to each other by the same amount,and the sheet is fed based on the center of the sheet cassette 1 usingthe side regulating members 7 and 8. The movable member 13 is moved topress the sheet S2 against the fixed member 19, thereby regulating oneof the side end positions of the small-size sheet S2. That is, in theembodiment, the movable member 13 and the fixed member 19 are sandwichedbetween the side regulating members 7 and 8 that feed the sheet based onthe center of the sheet cassette 1, thereby feeding the small-size sheetS2 based on one side of the fixed member 19.

Further, in the embodiment, the intermediate plate 6 is provided whilebeing movable in the width direction with respect to the cassette body5. Therefore, even if the dedicated cassette 30 is fixed to theintermediate plate 6, the dedicated cassette 30 can be moved in thewidth direction, and the position of the small-size sheet S2 can bechanged in the width direction.

When the intermediate plate 6 is moved in the width direction, thesmall-size sheet S2 that is moved based on one side of the sheetcassette 1 can be fed based on the center of the sheet cassette 1. Whenthe intermediate plate 6 is fixed to the cassette body 5 in the widthdirection, the same effect can be obtained even if the dedicatedcassette 30 is attached while being movable in the width direction withrespect to the intermediate plate 6.

As illustrated in FIG. 10, sometimes an interference member 41 existsabove the dedicated cassette 30. When the interference member 41 exists,the number of small-size sheets S2 is decreased to lift the intermediateplate 6, the movable member 13 is lifted along with the dedicatedcassette 30 as the intermediate plate 6 is lifted, and the movablemember 13 is brought in abutting contact with the interference member 41from below.

At this point, as described above, the movable member 13 can be swungabout the shaft 44 of FIG. 7 in the direction in which the intermediateplate 6 is lifted and lowered. Therefore, the movable member 13 isbrought in abutting contact with the interference member 41 and, asillustrated in FIG. 11, the movable member 13 is swung downward aboutthe shaft 44 against the biasing force of the spring 12 of FIG. 7.Because the number of small-size sheets S2 becomes small when theintermediate plate 6 is lifted, the regulation in the width direction ofthe small-size sheet S2 is maintained even if the movable member 13 isswung.

The intermediate plate 6 is lifted when the sheet is run out in thesheet cassette 1. When the sheet cassette 1 is drawn in the widthdirection to refill the sheet while the intermediate plate 6 is lifted,sometimes the dedicated cassette 30 attached to the intermediate plate 6in the lifted state collides with another component of the printer mainbody 50A. In such cases, when the dedicated cassette 30 collides withanother component, desirably a slope 42 in which the sheet cassette 1can be drawn while the intermediate plate 6 is gently pushed down isplaced in the fixed member 19 or the sheet stacking portion 14.

In order to improve usability, sometimes a positioning mechanism isprovided in the sheet cassette 1 in order to position the sideregulating members 7 and 8, when the side regulating members 7 and 8 aremoved to the positions that regulate the standard-size sheet. Inregulating the standard-size sheet, when the positions of the sideregulating members 7 and 8 are close to the position at which thededicated cassette 30 is used, sometimes the side regulating members 7and 8 are moved according to the positioning of the dedicated cassette30.

Possibly, the small-size-sheet regulating effect is reduced, when theside regulating members 7 and 8 are moved according to the positioningof the dedicated cassette 30 although the small-size sheet S2 isregulated. Therefore, when the positions of the side regulating members7 and 8 are close to the position at which the dedicated cassette 30 isused, desirably the positions of the side regulating members 7 and 8when sandwiching the dedicated cassette 30 are set so as to avoid thepositioning point performed by the positioning mechanism.

As described above, the positions of the movable member 13 and fixedmember 19 of the dedicated cassette 30 are regulated by the sideregulating members 7 and 8, so that the sheet can stably be fed with thesimple configuration without decreasing the strength of the intermediateplate 6.

In the embodiment described above, the intermediate plate 6 can be movedin the width direction with respect to the sheet cassette 1 or thededicated cassette 30 can be moved with respect to the intermediateplate 6 such that the sheet stored in the dedicated cassette 30 is fedbased on the center of the dedicated cassette 30. However, the inventionis not limited to the embodiment.

For example, sometimes the range where the intermediate plate 6 can bemoved is restricted with respect to the sheet cassette 1, or sometimesthe range where the dedicated cassette 30 can be moved is restrictedwith respect to the intermediate plate 6. In such cases, as illustratedin FIGS. 12 and 13, a dedicated cassette 30A may include a sheetstacking portion 14A and two movable members 13A and 13B that can bemoved in the width direction along the sheet stacking portion 14A.Therefore, with such configuration, even if the dedicated cassette 30Ais not moved in the width direction, the small-size sheet stored in thededicated cassette 30A can be fed based on one side of the sheetcassette 1 or the center of the sheet cassette 1.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2008-198732, filed Jul. 31, 2008, which is hereby incorporated byreference herein in its entirety.

1. A sheet feeding apparatus comprising: a sheet stacking portion onwhich sheets are stacked; a pair of first regulating portions that isprovided while being movable in a width direction of the sheet toregulate a position in the width direction of the sheets stacked on thesheet stacking portion; a sheet stacking unit that is attached to thesheet stacking portion; a pair of second regulating portions that isprovided on the sheet stacking unit to regulate the position in thewidth direction of the sheet stacked on the sheet stacking unit, and atleast one of the second regulating portions is movable in the widthdirection, wherein at least one of the sheet stacking portion or thesheet attacking unit is movable in the width direction, and the pair ofsecond regulating portions are regulated by the pair of first regulatingportions, respectively.
 2. The sheet feeding apparatus according toclaim 1, further comprising positioning portions, provided in the pairof second regulating portions while the sheet stacking unit is attachedto the sheet stacking portion, abutting the pair of first regulatingportions respectively, and wherein the positioning portions are equal toeach other in a distance from a sheet regulating surface of the secondregulating portion to a sheet regulating surface of the first regulatingportion.
 3. The sheet feeding apparatus according to claim 1, wherein asmall-size sheet whose position in the width direction cannot beregulated by the first regulating portion is stacked on the sheetstacking unit.
 4. An image forming apparatus comprising: an imageforming portion that forms an image in a sheet; and a sheet feedingapparatus that feeds the sheet to the image forming portion, wherein thesheet feeding apparatus includes: a sheet stacking portion on which thesheets are stacked; a pair of first regulating portions that is providedwhile being movable in a width direction of the sheet to regulate aposition in the width direction of the sheet stacked on the sheetstacking portion; a sheet stacking unit that is attached to the sheetstacking portions; a pair of second regulating portions that is providedon the sheet stacking unit to regulate the position in the widthdirection of the sheet stacked on the sheet stacking unit, and at leastone of the second regulating portions is movable in the width direction,wherein at least one of the sheet stacking portion or the sheet stackingunit is movable in the width direction, and the second regulatingportions are regulated by the pair of first regulating portions,respectively.
 5. The image forming apparatus according to claim 4,further comprising positioning portions, provided in the pair of secondregulating portions while the sheet stacking unit is attached to thesheet stacking portion, abutting the pair of first regulating portions,respectively, and the positioning portions are equal to each other in adistance from a sheet regulating surface of the second regulatingportion to sheet regulating surface of the first regulating portion. 6.The image forming apparatus according to claim 4, wherein a small-sizesheet whose position in the width direction cannot be regulated by thefirst regulating portion is stacked on the sheet stacking unit.